public class IsSubtree {
    class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
    }
    public boolean isSubtree(TreeNode root, TreeNode subRoot) {
        if (root == null) return false;
        if(isSameTree(root, subRoot)) {
            return true;
        }
        if(isSubtree(root.left, subRoot)) {
            return true;
        }
        if(isSubtree(root.right, subRoot)) {
            return true;
        }
        return false;
    }

    public boolean isSameTree(TreeNode p, TreeNode q) {
        if (p == null && q != null ||p != null && q == null)
            return false;
        if (p == null && q == null) return true;
        if (p.val != q.val) return false;
        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right);
    }
}
